Guesses and Proof.
A theory helpful to the observer or the experimenter comes at last, in many cases, from much guessing. The theorist fills his mind with facts, broods over them, endeavors to explain them, but whether his theory is true or false must be decided solely by proof. This point was clearly stated by Dr. Pye-Smith, of London, in his Harveian oration, 1893:—“As Paley justly puts it, he only discovers who proves. To hit upon a true conjecture here and there, amid a crowd of untrue, and leave it again without appreciation of its importance, is a sign, not of intelligence, but of frivolity. We are told that of the seven wise men of Greece, one (I believe it was Thales) taught that the sun did not go around the earth, but the earth around the sun. Hence it has been said that Thales anticipated Copernicus—a flagrant example of the fallacy in question. A crowd of idle philosophers who sat through the long summer days and nights of Attica discussing all things in heaven and earth must sometimes have hit upon a true opinion, if only by accident, but Thales, or whoever broached the heliocentric dogma, had no reason for his belief and showed himself not more, but less, reasonable than his companions. The crude theories and gross absurdities of phrenology are not in the least justified or even excused by the present knowledge of cerebral localization; nor do the baseless speculations of Lamarck and Erasmus Darwin entitle them to be regarded as the forerunners of Charles Darwin. Up to 1859 impartial and competent men were bound to disbelieve in evolution. After that date, or at least, so soon as the facts and arguments of Darwin and Wallace had been published, they were equally bound to believe in it. He discovers who proves, and by this test Harvey is the sole and absolute discoverer of the movements of the heart and of the blood.”